6 Answers
6

A wireless computer is capable of all the functions of any wired computer and often more, since any currently sold higher end computer will have wireless as a feature.

A wired computer is capable of most of the same functions. The principle difference is the need to run wiring around your bike. This is a minor issue if you only have a front wheel speed sensor, but if you add cadence, or also use a generator hub, then the wiring paths will be quite busy, and difficult to make "clean" in appearance on your pretty new bike.

I generally recommend a wireless computer. A quality brand will be very simple to set up. They basically require zip tying the sensors in place, ensuring that the magnet which trips the sensor circuit is in the right place in relation to the sensor, and spinning the wheel to pair the unit.

Every brand has slightly different pairing instructions, and the more feature filled and pricey the unit is, the more necessary it is to follow the directions step by step. Radio interference is an issue that some early units had, but that has long since been dealt with, by encrypting the radio signal, and only recognizing data from the correct encryption and frequency.

Another advantage of the wireless computer is that if you have more than one bike you only need a couple of extra sensors and the wireless computer can easily be swapped from one bike to another. The Garmin 500 (and probably others) allow 3 different bikes to be setup on the one trip computer.

In short, do the wireless. They are just as reliable, just as easy or easier to set up, and look better on the bike.

I think we need to be model specific here, I have had problems with erratic data and a few other people have noted that wireless does not work for them. Plus there is the problem of riding in groups where interference can be a problem, not all makes have a way around that, e.g. the VDO ones don't. I think the answer to the question has to be fairly brand/model specific if it is going to be wireless.
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ʍǝɥʇɐɯJul 31 '11 at 23:08

I think that any new/modern wireless computer that isn't bargain basement junk uses a coded signal option which eliminates interference from other computers and low power radio devices. I use Polar's CS 200 CAD, which a a fairly inexpensive computer for cadence and heart rate, and I've also used Garmin's Edge 305, 705, 500 and 800. I've used basic Cateye wireless systems, and I've used my iPhone with an ANT+ sensor.
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zenbike♦Aug 1 '11 at 4:24

I've not had the kind o problems all of you are describing with wireless computers in 10 years at least. If you do, I suspect old old/bargain basement computer choices, or setup issues. But as the setup is simple, I'd say you need to get out of the basement. Or buy a computer within the last 5 years, maybe. The only time I have ever had signal issues with a computer was when the batteries were so low as to not send one. A good computer is not just defined by wireless or not, but every high quality computer on the market currently, is wireless. Only the most basic of computers is wired at all.
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zenbike♦Aug 1 '11 at 4:27

What are you using for lighting? I use either a NiteRder Minewt 350 LED or a Light and Motion Stella 600, also a powerful LED. I'm currently using a Garmin Edge 800 on my MTB and a Polar CS500 Cadence on my road bike. I've used Cateye computers, Specialized, Trek, a half dozen other brands. I haven't had any issues at all in several years. I do remember having computers with these issues, and apparently the Polar stuff from a year or two ago had issues with LED lights. If you're currently having issues, I'd be curious what specific products you're using.
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zenbike♦Aug 1 '11 at 16:19

I've only ever used wired computers because they seemed more reliable. However, I have a friend who uses a wireless computer.

The biggest problem I've observed is that when he starts riding after a rest he has to make sure he 'wakes up' his computer otherwise it won't track the ride until he does. He's forgotten (and lost ride data) often enough that this is a big dealbreaker for me.

If the computer uses a sleep function like this, then there is an autostart option that he needs to turn on. So that he doesn't have to manually turn it on. Most also have a 30-45 minute window before they sleep, so that would be a long break.
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zenbike♦Aug 1 '11 at 4:29

No, I have the same problem with the Strada, and autostart is turned on. And it's very unpredictable as to when it will "sleep" and when not -- generally after overnight, if it sleeps it wakes right up on its own, but after a 30-minute stop it may not.
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Daniel R HicksAug 1 '11 at 10:54

The chief advantage of the wireless is that it doesn't have wires that you have to route, and which can get snagged. In fact, that's probably the only advantage.

When my old wired Cateye gave up the ghost (the cadence sensor basically fell apart), I bought a new Cateye Strada wireless unit, and it's been a bit of a PITA. First unit didn't work at all, so I returned that and got a second. It works, but setting it up the radio is non-trivial, and they saved 50 cents by putting the wheel and cadence sensors in one unit, so it's really tricky to get the pickup adjusted right. And on that unit the stupid one-button design causes the it to switch displays when you hit a bump, reset if you rest your hand on it for an instant.

(I don't understand why so few units have cadence anymore -- I use my cadence more than my MPH.)

Added: Finally solved the one-button-hit-a-bump problem by placing a tiny blob of silicone caulk between the unit and the bracket. Will make it hard to change the battery when the time comes, but I'll probably replace the entire unit then anyway -- the Strada sucks.

Can't tell for sure if that one's any better than the Strada. They don't say outright whether it has one pickup or two, and it looks from the picture like the pickup is attached with zip ties, just like the Strada. And the cadence display is apparently only available in the lower small display row.
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Daniel R HicksAug 1 '11 at 21:21

2 pickups. I haven't used the Cateye Strada, but they all are attached with zip ties, at least all that I've seen. Cadence position has options on my 2 year old model, but the current one may change that.
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zenbike♦Aug 2 '11 at 3:10

I currently have a wireless unit and I like it a lot. One thing I don't like about it is that the wheel sensor is quite a bit larger than the wired units, because it has to have a place for the battery, which is a large CR2032. One wireless unit I had in the past would show I was travelling (quite fast actually) when stopped at a traffic light. I figured this was due to the sensor loop. My current unit doesn't have the problem. They were both relatively cheap units so I'm not sure why the difference.

For the most part, I've found that wireless units work pretty well. The batteries in the screen usually die before the battery in the sensor, so I just replace them at the same time, so that I don't have to worry about the sensor cutting out. I currently have a Louis Garneau which I found was quite reasonably priced. Some of the cheaper units have very few functions, which is something you should watch out for. The first wireless unit I had (CatEye brand) didn't even give average speed, so you had to note down your start and stop times if you wanted to figure this out. The one I have now has quite a few features, although it lacks a Cadence meter. However, that isn't something I'm too interested in as I can usually tell if I'm working hard enough based on the speed and riding conditions

Thanks for your comments. They have all been very helpfull. I think that it's time I will also go wireless, reading the comments I have a feeling that accuracy and reliability are not a factor any more. And as I am buying a new pair, it's time to move a head.
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SaarikoAug 1 '11 at 5:58

Most bike computers are really at the tech level of a 1980's digital watch, which is fine if you just want the time, speed and distance functions. I have got a drawer full of dead ones somewhere. The most useful functions beyond the basics are cadence and altitude. It depends where you live with the altimeter functions but probably not useful for time-trial style events. For me though, particularly if touring it is really useful to know how much height you have in the bank.

If you are doing indoor training on rollers you will need a sensor on the back wheel, that is what you get with cadence measurement computers.

As for wireless versus wired, the problem I have had with entry level wireless is that they lie. There is a loop to stop the trolleys escaping from Tesco's car park that sets my speedometer as going at 99+ mph. That is annoying as I like to get my maximum speed and average speed yet what I get from the speedometer is useless.

You can start out with a basic wired Cateye/Sigma with cadence and spare bracket to put on your other bike. Further down the line when you get heart rate monitor and need data download link you will be able to make a better decision on what to get based on your needs. To explore the high end bicycle telemetry options you can look up what they have on the Tour de France these days.

As I recall, you input the wheel/tire size and you measure distance traveled (around ten feet or so).
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Neil FeinAug 1 '11 at 22:50

Measuring distance traveled is a way to refine tire size, but most units tell you how to do that, though they may require you to look up the distance in a table rather than inputting it directly. Even without the table its good ole "two pies are not square".
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Daniel R HicksAug 2 '11 at 11:20

The problem is not as much from calibration as it is from radio and magnetic interference. A lot of heavy equipment like large air conditioners or generators send out signals that get picked up by a lot of wireless bike computers. I know several spots that tell me I'm going 50+ mph when standing still.
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captncraigAug 2 '11 at 20:47

Another consideration for wireless sensors is that they have batteries that are (usually) not replaceable (at least the Polar unit I have). This means that you have to replace the sensors when the batteries run out. Granted, this has no happened to me yet, several thousand miles in.

Wired sensors use a simple circuit wherein the wire carries two halves of a circuit. The sensor has a small magnetic reed switch that gets closed when the magnet on the wheel passes.